1. Field of the Invention
The present invention relates to a thin film transistor substrate applied to a display device and a fabricating method thereof, and more particularly to a thin film transistor substrate adapted to simplify processing, and a fabricating method thereof.
2. Description of the Related Art
A liquid crystal display device controls the light transmittance of liquid crystal having dielectric anisotropy by use of an electric field to display a picture. For this, the liquid crystal display device includes a liquid crystal display panel for displaying a picture through a liquid crystal cell matrix and a drive circuit for driving the liquid crystal display panel.
Referring to FIG. 1, a liquid crystal display panel of the related art includes a color filter substrate 10 and a thin film transistor substrate 20 which are bonded together with a liquid crystal 24 therebetween.
The color filter substrate 10 includes a black matrix 4, a color filter 6 and a common electrode 8 sequentially formed on an upper glass substrate 2. The black matrix 4 is formed in a matrix shape on the upper glass substrate 2. The black matrix 4 divides the area of the upper glass substrate 2 into a plurality of cell areas where a color filter 6 is formed. The black matrix 4 prevents light interference between adjacent cells and external light reflection. The color filter 6 is divided by the black matrix 4 into red R, green G and blue B filters in the cell area that transmit red, green and blue light. The common electrode 8 supplies a common voltage Vcom when driving liquid crystal 24, to a transparent conductive layer (not shown) formed over the entire surface of the color filter 6. An overcoat layer (not shown) is further formed between the color filter 6 and the common electrode 8 in order to planarize the color filter 6.
The thin film transistor substrate 20 includes a thin film transistor 18 and a pixel electrode 22, both formed at each cell area defined by the crossing of a gate line 14 and a data line 16 in a lower glass substrate 12. The thin film transistor 18 supplies a data signal from the data line 16 to the pixel electrode 22 in response to a gate signal from the gate line 14. The pixel electrode 22 is formed of a transparent conductive layer and supplies the data signal from the thin film transistor 18 to drive liquid crystal 24.
The liquid crystal 24 having dielectric anisotropy rotates according to an electric field formed by the data signal of the pixel electrode 22 and the common voltage Vcom of the common electrode 8 to control light transmittance. Thus, gray level may be realized.
The liquid crystal display panel further includes a spacer (not shown) for uniformly maintaining a cell gap between the color filter substrate 10 and the thin film transistor substrate 20.
The color filter substrate 10 and the thin film transistor substrate 20 of the liquid crystal display panel are formed by a plurality of mask processes. One mask process includes a plurality of processes such as a thin film deposition process, a cleaning process, a photolithography process (hereinafter, referred to as “photo-process”), an etching process, a photo-resist peeling process, and an inspection process, etc.
The thin film transistor substrate 20 includes a semiconductor process and requires a plurality of mask processes. Thus, its fabricating process is complicated and is a large factor in the increase of manufacturing cost of the liquid crystal display panel. Accordingly, there is a need to reduce the number of mask processes in fabricating a thin film transistor substrate.